The present invention relates generally to a plasma display panel (PDP) used in a flat panel type television set, a display for displaying information, and the like and a method of driving the plasma display panel. More particularly, the present invention relates to a plasma display panel which has high resolution and high luminance, and to a method of driving such plasma display panel.
A plasma display is a display device which displays an image and so on by exciting fluorescent substance by using ultraviolet rays produced by gas discharge to emit light. The plasma display is expected to be applied to a large picture size television set, an information display, and the like.
Various types of color plasma displays have been developed. As typical types of the color plasma displays, there are a DC pulse memory type display and an AC memory type display. At present, the AC memory type is mainly used because of the lifetime and the luminous efficiency. The AC memory type display is also categorized into an opposed electrode discharge type, a surface discharge type, and the like, depending on the cell structure, the electrode structure and so on. In particular, a reflection type AC surface discharge type plasma display is superior in the luminance, easiness of panel fabrication, and the like.
FIGS. 16A through 16C illustrate a panel structure of a typical reflection type AC surface discharge color plasma display. FIG. 16A is an elevational structural view in which a portion of a rear substrate 200 is cut away. FIG. 16B illustrates a structure at a cross section of a front substrate 100. FIG. 16C illustrates a structure at a cross section of the rear substrate 200.
The front substrate 100 which is on the side of a viewer comprises a glass substrate 1 and many band shaped transparent electrodes 3 formed in parallel on the glass substrate 1, in a horizontal direction. On each of the transparent electrodes 3, a bus electrode 4 is formed which bus electrode 4 is a band shaped narrow electrode to lower resistance of the transparent electrode 3. The transparent electrodes 3 are formed of a thin film of ITO (Indium Tin Oxide) or tin oxide. However, the resistance of each transparent electrode 3 should be sufficiently small in order to conduct a discharge current sufficient to emit light in a large size panel, and, therefore, the bus electrode 4 made of metal having good conductivity is attached to each of the transparent electrodes 3 to lower the resistance thereof. The bus electrode 4 is made, for example, of a thick film of silver or a thin film of copper, aluminum, or chromium, and is formed on the transparent electrode 3 near the side of a non-discharge gap 12 where intensity of light emission is low.
On such structure including the transparent electrodes 3 and the bus electrodes 4, a dielectric layer 7 and a protective layer 8 are formed. The dielectric layer 7 is fabricated by applying a low melting point glass paste on the structure including the electrodes 3 and 4, and thereafter baking it at a temperature near 600 degrees Celsius. Thereby, the dielectric layer 7 is formed as a transparent insulating layer having a thickness of approximately 20 through 40 microns. The protective layer 8 is formed by vacuum evaporation and the like, and formed of a thin film of magnesium oxide (MgO) which has a large coefficient of secondary electron emission and has a superior anti-sputtering characteristic.
The rear substrate 200 comprises a glass substrate 2 on which band shaped data electrodes 5 are formed in a vertical direction and, thereafter, a dielectric layer 10 having low melting point glass as the basis is formed thereon. Thereafter, band shaped isolation walls 6 are formed in a vertical direction on the dielectric layer 10. Then, at a bottom portion and sidewalls of each groove formed by the isolation walls 6, powder type fluorescent substance 9 of red, green and blue colors are sequentially applied, and thereby the rear substrate 200 is completed. The isolation walls 6 secure discharge spaces, and serve to prevent cross talk of discharge and to prevent blotting of emitted light. Approximately, the isolation walls 6 are 30 through 100 microns in width and 80 through 200 microns in height.
The above-mentioned front substrate 100 and the rear substrate 200 are opposed to each other such that the protective layer 8 of the front substrate 100 is opposed to the isolation walls 6 of the rear substrate 200. Both substrates 100 and 200 are then sealed at the periphery thereof by a fritted glass to obtain a panel assembly. The panel assembly is heated and evacuated, and discharge gas having rare gas as the basis thereof is introduced, thereby the plasma display panel is completed.
On the front substrate 100, the transparent electrodes 3 with the bus electrodes 4 are disposed in pairs having a surface discharge gap 11 therebetween. One of the pair of transparent electrodes 3 with bus electrodes 4 is used as a scanning electrode 13, and the other of the pair is used as a retaining or holding electrode 14. Between the pairs of transparent electrodes 3 with bus electrodes 4, the non-discharge gaps 12 each having a relatively large width are provided to avoid cross talk of discharge. Various voltage wave signals are applied to three kinds of electrodes, including the data electrodes 5 mentioned above, in addition to these scanning electrodes 13 and the retaining electrodes 14, thereby the plasma display panel is driven to perform display operation.
FIG. 17 shows an example of waveforms of fundamental drive signals for the AC surface discharge type plasma display panel. Scanning pulses Sc1, Sc2, . . . , ScN are sequentially applied to the scanning electrodes 13-1, 13-2, . . . , 13-N. At the same timing as that of each of the scanning pulses Sc1, Sc2, . . . , ScN, a data pulse Dp is sequentially applied to each of the data electrodes 5 corresponding to a data to be displayed at each display cell. The data pulses have a polarity opposite to that of the scanning pulses. Thereby, a discharge, that is, an opposing electrode discharge, occurs between the scanning electrode 13 and the data electrode 5 opposing to each other. Also, the opposing electrode discharge triggers occurrence of the surface discharge between the retaining electrode 14 and the scanning electrode 13, thereby writing operation is completed. Due to the surface discharge, i.e., a writing discharge, wall charges are produced on the surfaces over the scanning electrode 13 and the retaining electrode 14. In a cell in which wall charges are formed, retaining discharge of the surface discharge, i.e., retaining surface discharge, occurs by retaining pulses Re applied between the retaining electrode 14 and the scanning electrode 13. However, in a cell into which data is not written, retaining discharge does not occur even if the retaining pulses Re are applied, because there is no superimposing effect of electric fields caused by the wall charges. By applying the retaining pulses predetermined times, display of image and so on by light emission is performed.
Also, in order to improve write operation characteristic, a preliminary discharge operation is performed in which a high voltage is applied to all cells before performing write operation, so that any previously stored signals of the cells are erased and discharge is performed forcibly. In FIG. 17, Pd designates a preliminary discharge pulse, and Pe designates preliminary erasure discharge pulse.
As mentioned above, drive operation of a plasma display panel comprises a series of preparing operation, write operation and retained light emission operation. In FIG. 17, a series of such driving operation is shown as an example, in which driving operation of a plasma display panel is separated into a preparing interval in a whole panel, a write interval and a retaining interval. Various driving systems other than the above-mentioned system in which write operation and retain operation are separated can be used, for example, it is possible to use a system in which these operations are mixed. However, when considered in an individual display cell, it is common to these systems that, after preparing operation, write operation is disposed and then retaining operation is disposed.
When tone or gradation of an image and so on is to be displayed in a plasma display panel, a so-called xe2x80x9csub-field methodxe2x80x9d is used. In the AC type plasma display, it is difficult to modulate luminance of display emission by using voltage control, and, in order to modulate luminance, it is necessary to change number of times of light emission. In the sub-field method, an image of one page is divided into a plurality of pages of binary images and these binary images are continuously displayed in a high speed so that, by using integrating effect of vision, an image having multiple gradation is reproduced.
However, the above-mentioned prior art plasma display panel has the following disadvantages.
Although the surface discharge type AC plasma display panel has a superior display characteristic, as seen from the structure of the surface discharge electrodes shown in FIG. 16A through FIG. 16C, this plasma display panel needs a pair of electrodes for light emission of one pixel row. The width of each of the surface discharge gaps 11 is approximately 50 through 100 microns and is relatively narrow. However, the non-discharge gap 12 between adjacent pixel rows, that is, between an upper pixel row and a lower pixel row, should be relatively wide to avoid cross talk of discharge. Usually, it is necessary that the width of the non-discharge gap 12 is approximately two or three times as that of the surface discharge gap 11. It is also necessary that the width of each bus electrode 4 made of a metal has a width of approximately 100 microns or more due to the limitation of specific resistance of the metal of the bus electrode 4 and of fabrication technology. By these restrictions, it becomes difficult to increase the area of the electrodes themselves, and to enlarge optically opening portions where light emitted from the fluorescent substance 9 is not obstructed. Therefore, in a plasma display panel having a high resolution and a narrow pixel pitch, it becomes difficult to realize high luminance.
Also, as the resolution of a plasma display panel becomes high, a number of pixel rows becomes large and it is necessary to shorten a scanning time required for writing data into pixels of one row. As a scanning time for one row, approximately 3 microseconds are usually permissible in a usual television system, for example, an NTSC system, or in VGA system having 480 rows, even if a full color image is displayed by using the sub-field method. However, in the high-vision television system or a high resolution digital television system each having approximately 1000 pixel rows, it is necessary to surely perform writing operation within a scanning time equal to or shorter than approximately 1.5 microseconds. To realize the write operation in such a short time, a high speed drive of a plasma display panel is one of major concerns.
As a measure of improving the above-mentioned items, there is provided a plasma display panel in which an isolation wall is provided in a central portion of each of wide transparent electrodes and thereby decreasing a number of the transparent electrodes by half. FIG. 18A illustrates a cross sectional structure of such plasma display panel. As shown in FIG. 18A, a bus electrode 4 is provided in the central portion of each of wide transparent electrodes 3, and an isolation wall 15 is disposed over each of the bus electrodes 4. Also, FIG. 18B illustrates a cross sectional structure of a conventional commonly used plasma display panel for reference. In the structure of FIG. 18A, the non-discharge gaps 12 in the plasma display panel shown in FIG. 18B are not provided, and a proportion of aperture, or an optically opening portion where light emitted from the fluorescent substance 9 is not obstructed, can be made relatively large. Therefore, it is expected that display having a high luminance can be realized. However, there is a disadvantage that the isolation walls 15 can not easily be fabricated. Also, when the isolation walls 15 are disposed in addition to the isolation walls 6 which are disposed in stripes and which are disposed perpendicular to the surface discharge electrodes, evacuation conductance is decreased greatly in a manufacturing process and, therefore, panel characteristics are deteriorated.
Considering the problems mentioned above, the present invention has been thought out.
It is an object of the present invention to obviate the disadvantages of conventional plasma display panels.
It is another object of the present invention to provide a plasma display panel in which a decrease in luminance accompanied by an increase in resolution can be improved.
It is still another object of the present invention to provide a plasma display panel in which difficulty in driving the plasma display panel caused by an increase in resolution can be obviated.
It is still another object of the present invention to provide a plasma display panel which has high resolution, but which has a simple structure and is inexpensive.
According to an aspect of the present invention, there is provided a plasma display panel comprising: a plurality of center slit surface discharge electrodes extending in a first direction, each of the center slit surface discharge electrodes having a pair of surface discharge electrode portions and a center slit between the surface discharge electrode portions; surface discharge gaps each formed between adjacent the center slit surface discharge electrodes; and a plurality of data electrodes extending in a second direction which crosses the first direction of extension of the center slit surface discharge electrodes.
In this case, it is preferable that each of the center slit surface discharge electrodes comprises the pair of surface discharge electrode portions which are formed of a pair of transparent electrodes and which are disposed parallel to each other via the center slit, and a bus electrode which electrically couples the pair of transparent electrodes with each other.
It is possible to provide the plasma display panel with isolation walls which are disposed parallel with the data electrodes and which define discharge spaces for display cells.
It is also preferable that the bus electrode comprises a pair of elongated bus electrode portions which are disposed parallel to the center slit on the pair of transparent electrodes and which are mutually connected on both ends thereof at the locations outside the center slit surface discharge electrode, thereby the pair of the transparent electrodes are mutually electrically coupled via the bus electrode.
In this case, the pair of elongated bus electrode portions can be electrically coupled via a plurality of coupling portions formed at locations facing the isolation walls, thereby the bus electrode constitutes approximately a ladder shaped conductor.
It is preferable that the bus electrode has approximately a serpentine shape and electrically couples the pair of transparent electrodes with each other via portions of the bus electrode extending approximately in the second direction and extending at locations facing the isolation walls.
Also, it is preferable that each of the pair of transparent electrodes is divided into a plurality of approximately oblong card shaped portions which are separated at locations facing isolation walls.
Further, it is preferable that each of the pair of transparent electrodes has approximately comb like shape in which a plurality of cut in portions are provided approximately at locations facing isolation walls from the surface discharge gap side toward the center slit side.
It is preferable that the pair of transparent electrodes have a pair of band shaped portions and a plurality of coupling portions which are located in the center slit and which electrically couple the band shaped portions at the locations facing the isolation walls, and the bus electrode is a band shaped bus electrode which is disposed approximately in the central portion of the center slit and which is electrically coupled with the plurality of coupling portions.
It is also preferable that the bus electrode is a fish-bone shaped bus electrode which is disposed approximately in the central portion of the center slit and which has a plurality of branch portions extending in the second direction at locations facing the isolation walls, and the pair of transparent electrodes are electrically coupled with each other via the plurality of branch portions.
It is possible for each of the data electrodes to have wide portions in the proximity of the surface discharge gaps between adjacent the center slit surface discharge electrodes, and to have narrow portions in the proximity of the center slits.
It is also possible to provide a colored layer is formed in the proximity of each of the center slits.
It is preferable that the center slit surface discharge electrodes are grouped alternately into S electrodes and C electrodes, a scanning driver for applying scanning pulses is connected to each of the S electrodes, and the C electrodes are grouped into a group of C electrodes of odd number and a group of C electrodes of even number, each of the groups of C electrodes being electrically coupled together.
According to another aspect of the present invnetion, there is provided a method of driving a plasma display panel comprising: providing a plurality of center slit surface discharge electrodes extending in a first direction, each of the center slit surface discharge electrodes having a pair of surface discharge electrode portions and a center slit between the surface discharge electrode portions; providing a plurality of data electrodes extending in a second direction which crosses the first direction of extension of the center slit surface discharge electrodes; forming surface discharge gaps each between adjacent the center slit surface discharge electrodes; and performing data write operation between the center slit surface discharge electrodes and the data electrodes by applying scanning pulses to the center slit surface discharge electrodes and by applying data pulses to the data electrodes depending on data to be displayed, thereby performing display operation.
It is preferable that the method further comprises: grouping the center slit surface discharge electrodes alternately into C electrodes and S electrodes; connecting a scanner driver to each of the S electrodes, the scanner driver supplying the scanning pulses; grouping the discharge gaps to be driven for display to those of odd field and of even field; in the odd field, applying the scanning pulses to the S electrodes of odd number to perform write operation between the S electrodes and the data electrodes; in a retaining period of the scanning pulse, alternately applying retaining pulses to the S electrode and the C electrode of a pixel row of odd number which corresponds to the odd field; applying in phase signals to the S electrode and the C electrode of a pixel row of even number which corresponds to the even field, thereby performing retained discharge of the pixel row of odd number; in the even field, applying the scanning pulses to the S electrodes of even number to perform write operation between the S electrodes and the data electrodes; in a retaining period of the scanning pulse, alternately applying retaining pulses to the S electrode and the C electrode of a pixel row of even number which corresponds to the even field; and applying in phase signals to the S electrode and the C electrode of a pixel row of odd number which corresponds to the odd field, thereby performing retained discharge of the pixel row of even number, thereby performing display operation in whole picture.
It is also preferable that the method further comprising: grouping the discharge gaps to be driven for display to those of odd field and of even field; in the odd field, applying the scanning pulses to the center slit surface discharge electrodes of odd number to perform write operation between the electrodes and the data electrodes; in a retaining period of the scanning pulse, alternately applying retaining pulses to the center slit surface discharge electrode of odd number and the center slit surface discharge electrode of even number; performing light emission by retained discharge which is the same in two rows in the pixel rows on both sides of the center slit surface discharge electrode of odd number into which write operation is performed; in the even field, applying the scanning pulses to the center slit surface discharge electrodes of even number to perform write operation between the electrodes and the data electrodes; in a retaining period of the scanning pulse, alternately applying retaining pulses to the center slit surface discharge electrode of even number and the center slit surface discharge electrode of odd number; performing light emission by retained discharge which is the same in two rows in the pixel rows on both sides of the center slit surface discharge electrode of even number into which write operation is performed, thereby performing display operation in whole picture.
It is further preferable that the method further comprises: grouping the discharge gaps to be driven for display into those of odd field and of even field; in the odd field, applying the scanning pulses to the center slit surface discharge electrodes of odd number to perform write operation between the electrodes and the data electrodes; in a retaining period of the scanning pulse, applying the same retaining pulses to the center slit surface discharge electrodes of even number adjacent to an upper portion or a lower portion of the center slit surface discharge electrode of odd number; alternately applying the retaining pulses whose phases differ by a half pitch to the center slit surface discharge electrodes of even number adjacent lower portion or upper portion of the center slit surface discharge electrode of odd number; performing light emission by retained discharge in the pixel row located on the lower or the upper side of the center slit surface discharge electrode of odd number; in the even field, applying the scanning pulses to the center slit surface discharge electrodes of even number to perform write operation between the electrodes and the data electrodes; in a retaining period of the scanning pulse, applying the same retaining pulses to the center slit surface discharge electrodes of odd number adjacent to an upper portion or a lower portion of the center slit surface discharge electrode of even number; alternately applying the retaining pulses whose phases differ by a half pitch to the center slit surface discharge electrodes of odd number adjacent to a lower portion or an upper portion of the center slit surface discharge electrode of even number; performing light emission by retained discharge in the pixel row located on the lower or the upper side of the center slit surface discharge electrode of even number, thereby performing display operation in whole picture.
It is also preferable that the above-mentioned various methods of driving a plasma display panel are switchable to perform display operation of a plasma display panel.